This invention relates to flexible polymer foam, more particularly to polyurethane foams having improved flame resistance and physical properties.
Flexible polymer foams are widely used in many applications, notably furniture and automobile seat padding. In these applications the burn characteristics of the foam are important. Flammability of the foam is therefore generally minimized to the extent possible.
Various methods are known to reduce the flammability of polymer foams. Commonly, additives such as aluminum trihydride or phosphous-containing compounds are incorporated into the foam for this purpose. Alternatively, halogenated polyols, especially brominated polyols such as dibromoneopentyl glycol, are used to increase the flame resistance in the foam. None of these additives have proved entirely satisfactory.
It is known that the incorporation of trimerized polyisocyanates (i.e. isocyanaurates) into a foam improves its burn characteristics. For example, trimerized toluenediisocyanate (TDI) has been used to prepare flexible foams. Although these foams do exhibit good foam characteristics, they also have poor physical properties, particularly poor compression sets and partial cell collapse. In addition, trimerized toluene diisocyanate tends to precipitate from the isocyanate solution in which it is dissolved, causing storage problems and a lack of uniformity in foams prepared therewith.
In U.K. Patent Specification No. 1,337,659, a solution of a cotrimer of TDI and a bis(4-isocyanatophenyl) methane (MDI) was used to prepare a flexible foam. No substantial improvement in the performance of this cotrimer solution relative to a TDI trimer solution was noted. The polyol used in preparing the film was not a polymer polyol, i.e. did not contain dispersed polymer particles.
Due to the deficiencies associated with previously known flexible polyurethane foams, it would be desirable to provide a foam having good burn characteristics as well as satisfactory physical properties.